Such a method and such a device are disclosed in [1]. This known procedure utilizes a motion estimation for picture information from picture areas of a number of temporally preceding pictures. A number of predecessor pictures are used for the motion estimation in order to make available a larger selection of picture areas, thereby improving the motion estimation and, associated with this, a motion compensation or an error concealment.
This can be explained, for example, by the fact that, in the case of background becoming free in a picture, between the picture that is to be coded or generally to be processed and its directly temporally preceding picture, a motion estimation is highly erroneous when only these two pictures are taken into account. However, if a number of predecessor pictures are taken into account in the context of the motion estimation or the error concealment, then it is possible to replicate these picture areas of the background becoming free from earlier, temporally preceding pictures.
Usually, in the case of so-called predictive coding methods, that is to say in the case of coding methods in which a so-called motion estimation is carried out, the present picture information is estimated from already transmitted picture information from picture areas and only a so-called estimation error produced as a result of the motion estimation is communicated. The more accurate this motion estimation, the more effectively the sequence of temporally successive pictures (also referred to as picture sequence hereinafter) can be compressed. To date, it has been customary to apply the motion estimation only to the directly temporally preceding picture. If objects move against a background of the picture, then the background becoming free cannot be predicted from the directly temporally preceding predecessor picture; rather, it must be coded completely anew. As a result, the efficiency of the picture compression decreases and the required data rate for transmission of the picture sequence with constant quality increases.
In the case of the procedure disclosed in [1], all of the predecessor pictures which are taken into account over a number of temporally preceding pictures in the context of the motion estimation are stored in their entirety. This leads to a considerable memory space requirement, particularly in applications in which only a relatively small memory space is available, for example in video telephony. In the case of this known procedure, a multiple of the memory space that is usually available for picture coding is required to store the necessary picture information of the multiplicity of temporally preceding pictures.
Consequently, the present invention is based on the problem of storing and processing picture information of temporally successive pictures, the quality of a motion estimation or an error concealment being similar to that as in the case of the procedure disclosed in [1], but the memory space requirement for storing the multiplicity of temporally preceding pictures being reduced.